Strain relief bushing



March 7, 1961 U P JR 2,974,186

STRAIN RELIEF BUSHING Filed Oct. 3, 1958 INVENTOR.

United States Patent STRAIN RELIEF BUSHING Ferdinand Klumpp, Jr., Union, NJ., assignor to Heyman Manufacturing Company, Inc.

Filed Oct. 3, 1958, Ser. No. 765,189

6 Claims. (Cl. 174-453) This invention relates to a self-locking strain-relief bushing which is adapted to securely lock an electrical conductor or cable in the bushing and to a plate or support in which the bushing is inserted.

Strain relief devices are employed in connection with various electrical appliances and apparatus, such as radio, television, and many other forms of electrical devices and apparatus, and serve to relieve strain upon the electrical conductor wires and cables so as to avoid possible severance from or impair proper connection of the conductor wires to terminals to which they are normally connected, and to also preclude damage to parts and avoidance of possible short circuits.

Strain relief bushings comprising two parts integrally joined are available. In one form, a longitudinal web extends along one side of the bushing providing a hinge. However, this form is not easy to handle. The hinge is stiff and rigid and not too flexible. Another form is provided with an end strap that connects adjacent ends but when assembled, protrudes past the ends of the bushing. Long connecting straps previously employed do not promote ease of molding. The longer the strap or hinge, the greater the chance for shrinkage.

It is an object of my invention to provide an improved self-locking strain-relief bushing which eliminates the disadvantages pointed out above.

Another object of my invention is to provide such a bushing which has all the desirable features of a two-part bushing but one in which the two halves or parts are integrally joined together and yet may be applied to a conductor or cable with ease preparatory to being mounted in an opening in a supporting member.

A still further object of my invention is to provide a one piece strain relief bushing in which a side strap is provided which readily permits assembly and which con-' forms to the shape of the assembled bushing.

A further object of my invention is to provide such a bushing which promotes ease of molding.

A still further object of my invention is to provide such an improved bushing which utilizes material usually wasted.

In accordance with my invention I provide a strain insulator having two parts integrally joined and having cooperating structures for locking the parts against longitudinal movement when assembled. Connected between registering ends of the two parts I provide a loop formed integrally with the two parts of the strain insulator. The loop extends from registering ends and transversely to the longitudinal areas of the strain relief bushing. One of the two parts of the bushing is cut away so that when the two parts are engaged the strap or loop is received within the projected surface of the part so that substantially no part of the strap extends beyond the boundaries of the bushing when assembled with a cord or a conductor. This facilitates assembly in the aperture of the supporting assembly. The strap is just long enough to permit the two parts of the bushing to be pivoted into engagement. The strap then does not interfere with 2,974,186 Patented Mar. 7,v 1961 insertion of the assembly through the aperture in the panel in which it is mounted. The strap also provides the runner during molding operations. It is thin enough to be very flexible, but strong enough not to break during handling.

The detailed description of my invention follows, reference being had to the drawing, in which:

Fig. l is a top plan view of a strain bushing made according to my invention;

Fig. 2 is a bottom view of Fig. 1;

Fig. 3 is a side elevation of the device shown in Figs. 1 and 2;

Fig. 4 is a left end view of Fig. 3;

Fig. 5 is a right end view of Fig. 3;

Fig. 6 shows the relationship of the two parts of the bushing preparatory to closing of a modification of the device shown in Figures 1 to 5;

Fig. 7 is a plan view of the bushing shown in Fig. 6 in its opened up relationship as taken from the mold;

Fig. 8 is a left end view of Fig. 7; and

Fig. 9 is a cross-section of a strain bushing using my invention positioned within the supporting member and clamped to a conductor.

A strain insulator made according to my invention comprises a body portion 10 and an insert or grip block 11 cooperating therewith forming a pair of cooperating shank sections tapering toward and integrally joined at their extremities. The body portion is provided with flat sides 20 and 21 to be received within an appropriate supporting member providing a properly shaped opening or aperture therein and has an end flange 22 which abuts against the surface of a supporting member when in use and has a depression or groove 23 adjacent the flange member into which the wall of the supporting member projects. The body portion may also be made elongated in transverse section as shown in Figs. 6, 7 and 8. The body member 10 is provided internally therein with a chamber 12 into which the grip block 11 is inserted in use. (See Figure 9.) The side walls of the body member 10 are provided with guide channels or grooves 14 and 15 which extend transversely of the longitudinal axis of the bushing. The chamber 12 is provided with end walls 16 and 17.

Received within the channel member is the insert or grip block 11 having elongated extensions or ribs 25 and 26 which are received within the channels 14 and 15. The member 11 is provided with a downwardly extending projection or tongue 28 which is provided with a recess for purposes to be described. This insert 11 is provided on its outside surface with a transverse groove or channel 27 oppositely disposed to groove 23 for receiving therein the wall of a supporting member. The insert is otherwise shaped to conform to the shape of the body member 10. In Figs. 6 to 8 inclusive, the primed numerals designate the same parts as the unprimed numerals 'in the other figures. As shown in Fig. 6, the grip block 11 is provided with the end walls 16" and 17".

In accordance with my invention I provide an elongated flexible strap or connection 30 formed integrally with the two parts of the bushing. While the strap is shown connected to one end of the bushing, it could as well be connected to the other end of the two-part bushing. However, for appearance sake, since the flange 22 is normally exposed, it is preferable to have the strap at the end opposite the flange. The strap is a short, straight strap or hinge. The bushing assembled within the supporting member 31 and engaging a conductor 32 is shown in cross-section in Fig. 9. I

As shown in Fig. 8, the strap 30' is joined to the body 10 in a recessed portion 10". As pointed out above, this permits the use of a very short strap. Though short,

the strap is flexible enough to permit the strap to be flexed in all directions, but which also is short enough to lie within the surface of the body projected. That is, the strap can be bent transversely of the longitudinal axis of the body member. This facilitates entrance of the extensions 25 and 26 into the'channels 14 and 15. Since the strap lies substantially within the projected surface of the body member 12, insertion of the bushing Within the panel is facilitated.

The connecting strap or loop is just long enough so that the parts may be moved relative to each other with ease in all planes to permit facility in inserting member 11 within member for gripping the cable. While the strap permits ease of handling, requiring the use of only one hand for holding the parts and cable during assembly, it does not interfere with the assembly since it lies substantially within the projected surface of the bushing. A further advantage of the shape of the loop is that it can be formed from the side runners which are utilized during molding of the bushing. This. has the advantage of making it unnecessary to strip the runners from the bushing and also conserves material which isnormally cut from the finished product. A bushing made according to my invention eliminates all the disadvantages pointed out above and provides a structure which facilitates the assembly of the bushing] with its clamped conductor and supporting structure, thus increasing efliciency during all operations relative to handling and. assembling the bushing in use.

What is claimed is:

l. A strain relief bushing of insulating material for holding an electrical conductor in a suitable aperture in a mounting member, comprising a body portion having a flange at one end to engage the mounting member on one side thereof and having a locking groove adjacent said flange, said bushing having a chamber, a grip block having substantially the same length as said body portion and fitting into said chamber, said grip block and body portion having cooperating means preventing relative longitudinal movement, a tongue on said grip block to extend into said chamber to grip a cable positioned within said channel, and an integral flexible connecting strap connected between registering ends of the body portion and the grip block for flexibly holding said body portion and grip block together to permit ready relative movement therebetween in all planes, said connecting strap being connected adjacent the outside surf-aces of said body portion and said body portion being recessed at one end, said strap being connected to said body portion in said recess, and having a width substantially less than the length of said bushing.

2. A strain relief bushing of insulating material for holding an electrical conductor in a suitable aperture in a mounting member, comprising a body portion having a flange at one end to engage the mounting member on one side thereof and having a locking groove adjacent said flange, said bushing having a chamber, a grip block having substantially the same length as said body portion and fitting into said chamber, a tongue on said grip block to extend into said chamber to grip a cable positioned within said channel, and an integral flexible connecting strap connected between registering ends of the body portion and the grip block for flexibly holding said body portion and grip block together to permit ready relative movement therebetween in all planes, said connecting strap being straight, said body portion being recessesd at one end, said strap being connected to said body portion in said recessed portion and extending transversely of the longitudinal axis of said bushing.

3. A one-piece strain relief bushing of molded plastic dielectric material adapted to be inserted axially and snapped into fixed position within the complementary aperture of a panel, said bushing including an axial shank comprising a pair of cooperating shank sections tapering toward and integrally joined at their entering extremities by a resilient hinge of reduced thickness to promote flexing thereof, the bending axis of which is parallel to the shank axis, said hinge serving to permit juxtapositioning of said shank sections for insertion within an aperture, a head portion associated with each shank section at the extremities oppositely disposed from the entering end thereof having an outwardly radiating surface for engaging one side of an apertured panel, shoulder means associated with at least one of said shank sections and spaced axially from the panel-engaging side of said head portion for engaging the opposite side of the panel, the juxtapositioned portions of the shank sections and said head portion having a longitudinal recess for accommodating an elongated conductor, and means extending from a wall defining said longitudinal recess for imping ing a conductor to secure it in clamped position within the bushing, said hinge being of sufliciently reduced width to be flexible in all planes, said hinge being straight, said body portion being recessed at one end, said hinge being connected to said body portion in said recessed portion and extending transversely of the longitudinal axis of said bushing.

4. An elongated strain-relief bushing of insulating material for holding an electrical conductor in a suitable aperture in a mounting member, comprising a body portion having a flange at one end to engage the mounting member on one side thereof, said body portion having a locking groove adjacent said flange on the outside thereof and a chamber therein, said body portion having a longitudinal channel therethrough communicating with said chamber, a T-shaped grip block having the longitudinal part of the T of substantially the same length as said body portion and fitting in said channel, the stem part of the T being adapted to extend into said chamber and having an end formation to grip a cable positioned within said chamber, the dimensions of the T being such as to cause the stem part of the T to force the cable toward the bottom of said chamber when the bushing is inserted into said suitable aperture in the mounting member, and an integral flexible connecting strap connected between the registering ends of the body portion and the grip block opposite said flange for flexibly holding said body portion and grip block together to permit ready relative movement therebetween in all planes, said connecting strap being straight, said body portion being recessed at one end, said strap being connected to said body portion in said recessed portion and extending transversely of the longitudinal axis of said bushing.

5. A one-piece strain relief bushing of molded plastic dielectric material adapted to be inserted axially and snapped into fixed position within a complementary aperture of a supporting panel, said bushing including a pair of cooperating shank sections tapering toward and integrally joined at their entering extremities by a resilient hinge, the bending axis of whioh is parallel to the shank axis, said hinge serving to permit juxtapositioning of said sections for insertion within an aperture, one of said sections having substantially greater circumferential extent than the other section and providing a longitudinal recess within which the other section interfits in clamped position, a head portion associated with each section at the extremities oppositely disposed from the entering end thereof having an outwardly radiating surface for engaging one side of an apertured panel, shoulder means associated with at least one of said sections and spaced axially from the panel-engaging side of said head portions for engaging the opposite side of the panel, the juxtapositioned portions of the sections and said head portions having a longitudinal passage for accommodating an elongated conductor, and means extending from a wall defining said passage for impinging a conductor to secure it in clamped position Within the bushing, one of said shank sections being provided with a recess, said resilient hinge being joined to said one of said shank sections in said recess, said 'hinge lying within the surface projected of said shank sections when said sections are in engaging relationship.

6. A one-piece strain relief bushing of molded plastic dielectric material adapted to be inserted axially and snapped into fixed position within a complementary aperture of a supporting panel, said bushing including a pair of cooperating shank sections tapering toward and integrally joined at their entering extremities by a resilient hinge, the bending axis of which is parallel to the shank axis, said hinge serving to permit juxtapositioning of said sections for insertion within an aperture, one of said sections having substantially greater circumferential extent than the other section and providing a longitudinal recess within which the other section interfits in clamped position, a head portion associated with each section at the extremities oppositely disposed from the entering end thereof having an outwardly radiating surface for engaging one side of an apertured panel, shoulder means associated with at least one of said sections and spaced axially from the panel-engaging side of said head portions for engaging the opposite side of the panel, the juxtapositioned portions of the sections and said head portions having a longitudinal passage for accommodating an elongated conductor, and means extending from a wall defining said passage for impinging a conductor to secure it in clamped position within the bushing, one of said sections having a recessed portion to which said hinge is joined, said hinge being just long enough to permit said means extending from a Wall to be received Within the cooperating shank section, said hinge lying within the surface projected of said sections and being joined intermediate the ends of said recessed portion.

References Cited in the file of this patent UNITED STATES PATENTS Klumpp July 29, 1947 Hultgren Aug. 7, 1951 Rapata July 14, 1959 

